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Model diseases
 

Model diseases

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  • The natural habitat of leptospires is the renal tubules of carrier animals. The animal hosts of leptospires are broadly categorized as carrier hosts, in whom the carrier state is temporary ranging from a few months to years, and reservoir hosts in whom the carrier state is life long. The reservoir hosts are the primary source of leptospires. They infect both animals and human beings. The carrier hosts who get infection either from reservoir hosts or from other carrier hosts can also act as the source of infection to human beings. Man to man transmission is very rare and leptospiral infection in human beings is a dead end of transmission chain. Therefore, the source of infection both in animals and humans is the carrier animal, though infection may actually occur through various environmental vehicles. There are two modes of transmission of the organism: the direct and indirect means. Direct transmission occurs when leptospires from tissues, body fl uids or urine of acutely infected or asymptomatic carrier animals enter the body of the new host and initiate infection. Infection may occur from direct contact with the tissues or urine of infected animals and occasionally through ingesting food contaminated with urine of infected animals or from droplet aerosol inhalation of contaminated fluids. Indirect transmission occurs when an animal or human being acquires leptospirosis from environmental leptospires, originating in the urine of excretor animals.Infection in humans may also occur indirectly when the bacteria come into contact with the skin (especially if damaged) or the mucous membranes. It can also result from contact with moist soil or vegetation that is contaminated with the urine of infected animals, or with contaminated water as a result of swimming or wading in floodwaters, accidental immersion or occupational abrasion. This is the most common way of infection with the leptospires. 
  • The environment plays a very important role in the transmission of the organism. In the tropical region where there is plenty of rainfall, it is often difficult to avoid exposure of the people to animals or contaminated environment especially since the bacteria is well adapted to the environment.  Although leptospires are susceptible to various environmental factors, particularly drying, acidic pH, salinity and presence of detergents and other bactericidal agents, they can survive for long periods in water and wet soil under favourable conditions. 
  • Antibiotic treatment is effective within 7 to10 days of infection and it should be givenimmediately on diagnosis or suspicion. Theantibiotic of choice is benzyl penicillin byinjection in doses of fi ve million units per dayfor fi ve days. Patients who are hypersensitiveto penicillin may be given erythromycin250 mg four times daily for fi ve days.Doxycycline 100 mg twice daily for 10 daysis also recommended. Tetracyclines are alsoeffective but contraindicated in patients withrenal insuffi ciency, in children and in pregnantwomen.Doxycycline has been used as a chemoprophylactic agent for short-term exposure4,but it cannot be recommended for routinecontinuous use or for long-term occupationalexposure5.

Model diseases Model diseases Presentation Transcript

  • MODEL DISEASES
  • SEASONAL INFECTIOUS DISEASES Leptospirosis
  • Causative Agent • • • • • • highly motile flexible helical or coiled aerobic bacteria with bent or hooked ends Spirochaeta icterohaemorrhagiae Yasuda et al. Deoxiribonucleic acid relatedness between seogroups and serovars in the family Leptospiraceae. Int J Sys Bacteriol 1987; 407-415
  • TRANSMISSION CYCLE OF LEPTOSPIROSIS DIRECT CONTACT • thru tissue or urine of infected animals • ingestion of contam food • droplet aerosol inhalation • contact with moist soil or vegetation contaminated with urine of infected animals INDIRECT CONTACT • swimming or wading in floodwaters • accidental immersion • occupational abrasion
  • Signs and Symptoms of Leptospirosis Icterus and hemorrhage Acute renal failure
  • Differential Diagnosis • Dengue • Rickettsial disease : Scrub typhus, murine typhus • Acute viral hepatitis • Sepsis • Influenza • Aseptic Meningitis
  • Problem with diagnosis • Low success rate of isolation • Unreliability of direct demonstration of leptospires in clinical samples using dark field microscopy • Inaccessibility of molecular techniques to most peripheral hospitals and clinics • Serological tests have low sensitivity during acute stage
  • Treatment • Early anti-microbial therapy is importantshorten the course and prevent carrier state • Choice : Penicillin G, Ampicillin • May cause “ Jarish-Huxheimer type reaction” • Mild cases oral Doxycycline or Amoxicillin
  • Prevention • Vaccination of domestic animals • Rodent control • Protective gloves and boots • Avoid swimming in contaminated waters • Vaccination in endemic region
  • Your Text Here PULMONARY TUBERCULOSIS
  • Pulmonary Tuberculosis • Tuberculosis (abbreviated as TB for tubercle bacillus or Tuberculosis) is a common and often deadly infectious disease caused by mycobacteria, m ainly Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs (as pulmonary TB).
  • Pulmonary Tuberculosis • Scanning electron micrograph of Mycobacterium tuberculosis
  • Epidemiology • Most common infectious cause of death worldwide • Latent phase of TB enabled it to spread to one third of the world population • 8,000,000 new cases each year • 3,000,000 infected patients die
  • Incidence • 1985-1990 TB cases increased 55% in Hispanics and 27% in African Americans • Populations at risk - Foreign-born individuals - Low socioeconomic status - Cancer pts - Celiac disease - Cigarette smokers - TNF-a antagonists - Corticosteroids • - HIV
  • Transmission • When people suffering from active pulmonary TB cough, sneeze, speak, or spit, they expel infectious aerosol droplets 0.5 to 5 µm in diameter. • A single sneeze can release up to 40,000 droplets. • People with prolonged, frequent, or intense contact are at particularly high risk of becoming infected, with an estimated 22% infection rate. • A person with active but untreated tuberculosis can infect 10–15 other people per year. • Others at risk include people in areas where TB is common,
  • Transmission
  • Transmission • people who inject drugs using unsanitary needles, • residents and employees of high-risk congregate settings, • medically under-served and lowincome populations, • high-risk racial or ethnic minority populations, • children exposed to adults in high-risk categories, • patients immunocompromised by conditions such as HIV/AIDS, people who take immunosuppressant drugs, • and health care workers serving these high-risk clients.
  • Diagnostics • Inject intradermally 0.1 ml of 5TU PPD tuberculin • Produce wheal 6 mm to 10 mm in diameter • Represent DTH (delayed type hypersensitivity)
  • Reading of Mantoux test • Read reaction 48-72 hours after injection • Measure only induration • Record reaction in mm
  • Classifying the Tuberculin Reaction as positive in • >5 mm is classified – HIV-positive persons – Recent contacts of TB case – Persons with fibrotic changes on CXR consistent with old healed TB – Patients with organ transplants and other immunosuppressed patients
  • Classifying the tuberculin reaction • >10 mm is classified as positive in – Recent arrivals from highprevalence countries – Injection drug users – Residents and employees of high-risk settings – Mycobacteriology laboratory personnel – Persons with clinical conditions that place them at high risk – Children <4 years, or children and adolescents exposed to adults in high-risk categories
  • Classifying the tuberculin reaction • >15 mm is classified as positive in – Persons with no known risk factors for TB
  • Factors may affect TST • False negative – Faulty application – Anergy – Acute TB (2-10 wks to convert) – Very young age (< 6 months old) – Live-virus vaccination – Overwhelming TB disease • False positive – BCG vaccination (usually <10mm by adulthood) – Nontuberculous mycobacteria infection
  • Chest Radiography • Abnormalities often seen in apical or posterior segments of upper lobe or superior segments of lower lobe • May have unusual appearance in HIVpositive persons • Cannot confirm diagnosis of TB!!
  • Chest radiography • No chest X-ray pattern is absolutely typical of TB • 10-15% of culture-positive TB patients not diagnosed by X-ray • 40% of patients diagnosed as having TB on the basis of x-ray alone do not have active TB
  • Specimen Collection • Obtain 3 sputum specimens for smear examination and culture • Persons unable to cough up sputum – induce sputum – bronchoscopy – gastric aspiration • Follow infection control precautions during specimen collection
  • Number of sputum samples required • overall diagnostic yield for sputum examination related to – the quantity of sputum (at least 5 mL) – the quality of sputum – multiple samples obtained at different times to the laboratory for processing • 3 samples obtained at least eight hours apart with at least one sample obtained in the early morning
  • Smear Examination • Strongly consider TB in patients with smears containing acid-fast bacilli (AFB) • Results should be available within 24 hours of specimen collection • Presumptive diagnosis of TB • Not specific for M. tuberculosis
  • AFB smear Mycobacterium tuberculosis (stained red) in sputum
  • Cultures
  • Signs and Symptoms
  • Signs and Symptoms • • Hemoptysis Also known as coughing up blood, it is a symptom of bleeding somewhere in the respiratory tract. Frothy and bright red blood may come from the nose, mouth, or throat (upper respiratory tract), the lower respiratory tract, or the lungs. The seriousness of the disorder depends on the cause of the bleeding.
  • Signs and Symptoms • Anorexia • The sysmptom of poor appetite whatever the cause
  • Treatment
  • Tuberculosis treatment • The standard "short" course treatment for tuberculosis (TB), is isoniazid, rifampicin, pyrazinamide, and ethambutol for two months, then isoniazid and rifampicin alone for a further four months. The patient is considered cured at six months (although there is still a relapse rate of 2 to 3%). For latent tuberculosis, the standard treatment is six to nine months of isoniazid alone. • If the organism is known to be fully sensitive, then treatment is with isoniazid, rifampicin, and pyrazinamide for two months, followed by isoniazid and rifampicin for four months. Ethambutol need not be used.
  • Drugs • 1. 2. 3. 4. 5. All first-line antituberculous drug names have a standard threeletter and a single-letter abbreviation: ethambutol is EMB or E, isoniazid is INH or H, pyrazinamide is PZA or Z, rifampicin is RMP or R, Streptomycin is STM or S.
  • Drugs • Daily Dose of TB Drugs
  • Drugs • Multi-drug resistant TB (MDR-TB) is defined as resistance to the two most effective first-line TB drugs: rifampicin and isoniazid. • Extensively drug-resistant TB (XDR-TB) is also resistant to three or more of the six classes of secondline drugs.
  • Monitoring and DOTS • • 1. 2. 3. 4. 5. DOTS stands for "Directly Observed Therapy, Short-course" and is a major plan in the WHO global TB eradication programme. The DOTS strategy focuses on five main points of action. These include government commitment to control TB, diagnosis based on sputum-smear microscopy tests done on patients who actively report TB symptoms, direct observation short-course chemotherapy treatments, a definite supply of drugs, and standardized reporting and recording of cases and treatment outcomes.
  • Prevention • TB prevention and control takes two parallel approaches. • In the first, people with TB and their contacts are identified and then treated. • Identification of infections often involves testing highrisk groups for TB. • In the second approach, children are vaccinated to protect them from TB.
  • Vaccines • Many countries use Bacillus CalmetteGuérin (BCG) vaccine as part of their TB control programs, especially for infants. According to the W.H.O., this is the most often used vaccine worldwide, with 85% of infants in 172 countries immunized in 1993. • BCG provides some protection against severe forms of pediatric TB • unreliable against adult pulmonary TB, • Currently, there are more cases of TB on the planet than at any other time in history • urgent need for a newer, more effective vaccine that would prevent all forms of TB—including drug resistant strains—in all age groups and among people with HIV.
  • Current Surgical Intervention • Patients with hemoptysis first received Bronchial Artery Embolization because of the recurrent hemoptysis. • Current indication of Lung Resection for pulmonary tuberculosis includes MDR-TB with a poor response to medical therapy, hemoptysis due to bronchiectasis or Aspergillus superinfection, and destroyed lung as previously reported, which are consistent with our indications. • Surgery remains a crucial adjunct to medical therapy for the treatment of MDR-TB and medical failure lesions.
  • Your Text Here PARASITIC INFECTIONS
  • PARASITIC INFECTIONS •Helminth – Schistosomiasis (parasitic worm) – Hookworm Disease •African Trypanosomiasis (“sleeping sickness”) •Cryptosporidiosis 46
  • Helminth • Schistosomiasis (bilharzia) - snailtransmitted, water-borne parasitic helminth • Hookworm - soiltransmitted infection caused by the nematode parasites Necator americanus and Ancylostoma duodenale 47
  • Hookworm • Hookworms live in the small intestine • Eggs are passed in the feces of an infected person. If the infected person defecates outside (near bushes, in a garden, or field) or if the feces of an infected person are used as fertilizer, eggs are deposited on soil • They can then mature and hatch, releasing larvae. Larvae mature & penetrate the skin of humans • Hookworm infection is mainly acquired by walking barefoot on contaminated soil or ingestion of larvae 48
  • Sonett72, Wikimedia Commons 49
  • Hookworm Symptoms: • Abdominal discomfort • Blood in the stool • Bloody sputum • Cough • Diarrhea • Fever • Itchy rash • Nausea/vomiting • Pale skin Most people have no symptoms once the worms enter the intestines 50
  • Hookworm Diagnosis Exams and Tests • CBC • Stool & parasite exam Joelmills, Wikimedia Commons 51
  • Treatment of Hookworm Treatment Goals: • Cure the infection • Treat complications of anemia • Improve nutrition • Parasite-killing medications such as albendazole, mebendazole, or pyrantel pamoate are usually prescribed • Increase protein in diet to reduce complications of anemia 52
  • Hookworm Prevention • Efforts to control hookworm infection include the sanitary disposal of feces and educational campaigns about the proper use of latrines • Wearing shoes can help to prevent the Hookworm larvae from penetrating the feet. Proper disposal of feces in areas away from habitations can prevent the occurrence of infective larvae in the environment 53
  • Hookworm Complications • Iron deficiency anemia caused by blood loss • Nutritional deficiencies • Protein loss with fluid buildup in the abdomen • High chance of reinfection 54
  • MODEL DISEASES